I've found that if I disconnect the tertiary monitor and connect the secondary via VGA it works fine at 1680x1050. It is limited to 1440x900 connected via DisplayPort with or without the tertiary monitor.

Any ideas on how to get this second monitor at the correct resolution? I'm wondering if it is my adapter. I thought that the DisplayPort to DVI adapter was supposed to be ok up to 1920x1200.

A colleague of mine suggests that you're expecting a lot from that card, and that may be the problem.
– user3463Nov 8 '10 at 21:25

I agree with Randolph but the one thing that comes to my mind is are all of your drivers as up to date as possible?
– Frank VNov 8 '10 at 21:37

@Randolph: What is your colleague basing that on? Does he or she have a link to support that claim? I'm curious because XFX's site says the card supports three monitor output, but I can't find details on what resolutions are supported when all three outputs are in use. (xfxforce.com/en-us/products/graphiccards/HD%205000series/…) @Frank: Yes, latest drivers from AMD have been installed.
– 80bowerNov 8 '10 at 22:04

@80bower - he's basing it on extensive experience. You may find that the max resolution is not supported for all three monitors.
– user3463Nov 8 '10 at 22:11

1

@80bower, you asked if it was your adapter. My colleague seems to think it is. That is all.
– user3463Nov 8 '10 at 22:19